High Definition TV

1
High Definition TV

• 2/08/2001
• Todd Owen
• Greg Daly
• Edmond Lam
• Presentation available at
• http//www.amnesiak.com/ee478/

2
Topics To Be Covered

• Explanation of Imaging Techniques
• Current TV Standards
• HDTV Formats
• HDTV Encoding
• HDTV Rollout
• Consumer Acceptance

3
Interlaced vs. Progressive Scan

• Interlaced scan is what common analog TVs use
  today
• Progressive scan is a very expensive HDTV feature
  that emulates film
• Interlaced formats NTSC (Americas), PAL
  (Europe), HDTV i
• Progressive formats HDTV p

4
Interlaced Scan

• A frame is made of two fields
• One field is comprised of odd horizontal lines,
  the other of even lines
• Display device interlaces the fields
• Done so TVs dont have to refresh as often
• US 59.94 fps, Europe 50 fps
• Interlacing causes motion tears and video look

5
Interlaced Scan Example
6
Progressive Scan

• No Fields frame is captured and displayed at
  once
• Film look and feel
• No motion tear
• More expensive!
• George Lucas Sony HDW-F900

7
Progressive Scan Example
8
Analog vs. Digital Transmission

• Analog transmissions can be easily distorted
• Digital transmissions error checking/correction
  (parity, CRC, encoding)
• The result no more ghosting, clarity more
  like satellite TV
• Occasionally may see some blocky artifacts
• For DVDs and home entertainment, the clarity will
  be near-perfect

9
Current TV Standard

• NTSC 50 years old
• Transmits signals as an electronic wave. In the
  wave, images and sounds are represented by
  continuously changing frequencies and voltage
  levels.
• Transmitters broadcast this signal over the air,
  and the waves are translated back into images and
  sounds by TV sets.
• The shape of this wave is susceptible to
  degradation as it travels to your home.

10
NTSC Composite Video

• Component to Composite Video Diagram
• Y - luminance information
• I,Q - color (chroma) information

NTSC
Y I Q

4.2 MHz LPF
R G B
Matrix
1.5 MHz LPF
X

3.58 MHz Osc.
0.5 MHz LPF
90? shift
X
11
NTSC and PAL Specs

• NTSC PAL
• Luma sampling frequency 13.5 MHz 13.5 MHz
• Chroma sampling frequency 6.75 MHz 6.75 MHz
• Frames/sec 30 25
• Luma active samples/line 720 720
• Chroma active samples/line 360 360
• Active lines/frame 480 576
• Sample resolution 8 bits 8 bits
• Data rate 166 Mb/s 166 Mb/s
• 30x720x480x8x2 25x720x576x8x2 166 Mb/s

12
Introduction to HDTV

• Formats
• Bandwidth
• Encoding and the digalog picture

13
HDTV Formats (ATSC std.)
14
TV and HDTV Bandwidth

• NTSC 6 MHz
• PAL 8 MHz
• Inefficient use of a very valuable spectrum
• Analog TV 378,000 pixels in 6 MHz
• HDTV up to 2,073,600 pixels plus Dolby 5.1 sound
  in 6 MHz!

15
Regulations and Governing Bodies

• FCC in the process of allocating frequencies
• What frequency is HDTV? There is no definite
  answer
• Trying to allocate frequencies within core
  areas, some markets will have uncommon
  frequencies
• By 2006, markets can reuse old analog channels

16
Signal Spectra
17
Signal Composition

• Uses computationally expensive Reed-Solomon ECC
• Note that spectrum is basically flat (90
  efficient!)

18
AC-3 MPEG-2

• HDTV Compression Methods

19
Dolby AC-3

• Perceptual Coding Compression
• Dolby Digital 5.1
• Decoding Format
• www.dolby.com/digital

20
Perceptual Coding

• Frequency ranges determined by human perception
• Masking

21
Dolby Digital 5.1

• 5 5 channels of full audio (3-20000 Hz)
• .1 low frequency channel (1-120 Hz)
• Sampling at 32, 44.1, 48 kHz

22
MPEG-2

• Motion Picture Experts Group
• MPEG-1, MPEG-2, MPEG-4
• Video Compression format, 551
• Motion Estimation Predictive Coding

23
MPEG-2 (cont.)

• Discrete Cosine Transform
• 8x8 Block
• Quantizing
• Hoffman/Run-Length Coding
• Zig-Zag or Alternate scan
• Take EE440-Introduction to Digital Imaging Systems

24
The MPEG-2 Process
Really Stripped Down Version
Quantize
DCT
VLC
Predictive Coding
25
DCT
DC
Low
8
Medium
High
8
26
DCT (cont.)
Quantize Matrix
DCT Block
Quantized DCT Block
8
16
19
64
24
19
8
1
1
16
16
22
21
16
14
1
1
0
19
22
26
41
5
27
2
0
1
Hypothetical Numbers
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Motion Estimation Predictive Coding

• I frames No prediction
• P frames Singular direction prediction
• B frames Bi-directional prediction
• Usual encoding pattern used IBBPBBPBBPBBPBB (15
  frames)

28
Hoffman/Run-length Coding
Zig-Zag for Progressive Scan
Alternate for Interlaced Scan
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Hoffman/Run-Length Coding (cont.)
Because DCT and Quantizing make most values in
the 8x8 matrix zero, Hoffman and run-length (VLC)
coding takes advantage of this by compacting all
the zeros.
12, 0, 0, 0, 3, 0, 0, 1, 2, 0, 0, 5, 00
12, (3,3) (2,1) (0,2) (2, 5), EOB
Looking in a predefined table for VLC we
translate our coded block into a bit stream. Now
instead of 8 bits x 64 pixels 512 bits, we get
something a lot smaller.
30
HDTV Rollout

• The Federal Communications Commission (F.C.C.)
  has mandated that all stations be capable of
  broadcasting HDTV by 2006.
• This will be done in a series of steps

31
Digital Television Transition Timeline

• November 1999Affiliates from the top 30 markets
  (which reach 50 percent of U.S. households) must
  have constructed digital facilities.
• December 1999Stations in some of the major
  markets, including New York, Los Angeles, Atlanta
  and Chicago, were broadcasting digital signals.
• May 2002The remaining markets after the top 30
  (there are 211 total) will have constructed
  digital facilities.
• April 2003All stations must simulcast at least
  50 percent of their NTSC programs on their
  digital TV channel.
• April 2004Stations must simulcast 75 percent of
  their NTSC programs on their digital TV channel.
• April 2005Stations must simulcast 100 percent of
  their NTSC programs on their digital TV channel.
• 2006The Federal Communications Commission has
  targeted this year for the complete conversion
  from analog to digital broadcasting.

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Conversion will be Expensive

• Consumers have to buy new equipment -- either a
  set-top box (to convert digital signals to analog
  signals) or a whole new TV set.
• Broadcasters have to spend a considerable amount
  of money to switch to HDTV. They have to buy new
  cameras, new titling and editing equipment, new
  tape machines, new rigs for their news vans --
  its a big investment.
• Cable operators have to convert all of their
  equipment and all of the set-top boxes in the
  home.
• Communities need to agree to have new towers
  built for broadcast channels.

33
Consumer Options

• LCD TVs
• Projection TVs
• CRT Tube TVs
• HDTV Converter
• HDTV vs. HDTV Ready

Most Expensive Least Expensive
34
Delivery Methods

• Over the air broadcasting
• Cable lines
• Satellite
• Currently only over the air broadcasting exists.
  Cable and satellite companies will be free to
  pick their own formats for broadcasting.